In Galatians 5: 22-23 Reina-Valera 1960 (NIV), the word of the Lord says:
22 But the fruit of the Spirit is love, joy, peace, patience, goodness, goodness, faith, meekness, temperance; Against such things there is no law.
Joy is part of the fruit of the Holy Spirit. This implies that every believer and even the church of Jesus Christ are called to experience the permanent and overflowing joy that comes from God through his Holy Spirit.
The psalmist David knew that in the presence of God "there is fullness of joy." This was the reason why David at dawn continually sought the presence of God.
The Word of God urges that "if someone is sad, they should pray." That is, he must seek the presence of God so that the joy of the Lord overflows in the heart of the Christian and all sadness is neutralized.
When the three wise men went to Bethlehem to see the child Jesus who was born, they were guided by the will of God, and God showed him the star that would guide them to Bethlehem; and when they "saw the star, they rejoiced with great joy" (Matthew 2:10).
Whenever the Christian does the will of God in any area of his life, he will end up experiencing the joy of the Lord.
When you make a true sacrifice for the love of God, a deep joy that fills your whole being invades you. This is explained by the Lord in the parable of the hidden treasure.
Matthew 13:44 New International Version (NIV)
44 Moreover, the kingdom of heaven is similar to a treasure hidden in a field, which a man finds, and hides it again; and glad for that, he goes and sells everything he has, and buys that field.
The hidden treasure is Christ. The man who finds it can be you or my person. Look at the magnitude of the sacrifice: he sold everything he had to acquire the hidden treasure (Christ).
How are you sacrificing yourself to keep the treasure hidden in your heart?
He says that this man, cheerful and excited to acquire the hidden treasure, ran to sell everything he owned.
If when he didn't have it, he was very happy to have it, how much greater joy should he feel now, knowing that he already has it?
This beautiful hidden treasure, which is Christ, is in the heart of every believer who has confessed to him. It implies, then, that there can be nothing that prevents the manifestation of joy in the Christian's life.
The Lord Jesus in his last speech to his disciples reiterated that his joy had been fulfilled in them (Jn 16:24).
Then, we can safely say that: "The joy of the Lord is our strength."